Objectives are to isolate and purify enzymes which recognize alkylated DNA bases and to define the extent of their action on DNA of subunits of chromatin. Purification of a procaryotic and a eucaryotic 3-methyladenine glycosylase continues and search for a procaryotic activity which recognizes 0-6 methylguanine. Quantitative and qualitative aspects of alkylation in vitro of nucleosomal DNA and the recognition of the alkylated bases by enzymes is under investigation. Repair of DNA treated with Beta-propiolactone is being examined.